A dandy roll is used in the manufacturing of paper. The purpose of the dandy roll is to smooth the paper and apply a finish to the paper as the paper moves under the dandy roll. The dandy roll eliminates bubbles, foam, and major inequalities in formation, compacts the fibers, and may mark the paper with a watermark pattern. In large paper making machines, the dandy roll is of considerable weight.
FIGS. 1 and 2 illustrate a dandy roll disclosed in U.S. Pat. No. 2,947,356. A dandy roll 10 includes an end plate 12 having an outwardly extending annular flange 14. At the opposite end of dandy roll 10 is an end plate 17 from which extends an integrally formed, elongated, hollow journal 18. Extending between end plate 12 and 17 is a framework (not shown) supporting a screen 20 which forms the surface of dandy roll 10 and may bear patterns for watermarking. A pair of rollers 26 are mounted on spaced brackets 22 by means of pins 24. An annular shoe 16 on dandy roll 10 is in rolling engagement with rollers 26. A bearing 28 supports hollow journal 18. Means for driving dandy roll 10 may be affixed to the outer end of journal 18, for example, a pulley, gear, or sprocket. FIG. 1 shows a sprocket 30 having a plurality of circumferential grooves 31 for reception of a plurality of driving V-belts (not shown). Flange 14 defines an opening in end plate 12 through which extends one of a support bar 32. Support bar 32 supports a water tray 40, also referred to as a dandy pan 40. Dandy pan 40 is fixed while dandy roll 10 is rotated thereabout. A spray pipe 42 provides liquid spray droplets to wash fibers and other paper debris from screen 20, through the openings in screen 20, and into dandy pan 40. The removal of the paper debris improves paper quality. The liquid and other debris is then removed from the dandy pan.
In the manufacturing of some types of paper, for example photographic paper, defects in the paper may adversely affect the use of the paper. Defects, such as damage to the paper finish, can occur should the liquid spray droplets be allowed to fall onto the paper. Further, moisture droplets which form on the dandy pan may also damage the paper finish should they fall onto the paper. Steam, circulated within the dandy pan, can be employed to provide a source of heat. The steam causes the dandy pan to dissipate sufficient heat energy to promote the evaporation of the moisture droplets and liquid spray droplets. The evaporation of the moisture droplets and liquid spray droplets reduces possible damage to the paper finish.
The steam circulated within dandy pan 40 can be extremely hot, for example, 225 degrees F. and 12 psi. When the liquid spray droplets fall onto dandy pan 40, cracks can occur on the surface of the dandy pan causing steam to escape. The escaping steam condenses on the paper surface, thereby adversely affecting the paper by contributing to a poor surface finish of the paper. Repairing and/or replacing the dandy pan eliminates the problem, but is expensive and reduces production. Cracks on the surface of the dandy pan have been a persistent problem. Applicant's have noticed cracks in the surface of a dandy pan within 6 to 12 months of operation.
Accordingly, a need continues to exist for a dandy pan suitable for a manufacturing environment. The dandy pan must be of a construction whereby cracks are not susceptible to forming on the surface of the dandy pan.